Rotary safety blade



H. F. DUNLAP ETA! ROTARY SAFETY BLADE i Filed March 5,

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INVENTORS HENRY F. DUN LAP LOYD R. KERN Attorney Nov. 5, 1963 H. F. DUNLAP ETAL 3,109,275

ROTARY SAFETY BLADE Fii'ed March 5, 1 s Sheets-Sheet 2 INVENTORS HEN F. DUNLAP BY LOY KERN Attorney 1963 H. F. DUNLAP ETAL ROTARY SAFETY BLADE Filed March 5, 1963 3 heetsh t 3 INVENTORS HENRY F. DUNLAP y LOYD R. KERN Attorney United States Patent 3,109,275 RGTARY SAFETY BLADE Henry F. Dunlap, Dallas, and Loyd R. Kern, Irving, Ten,

assignors to The Atlantic Refining (Iornpany, Philadelphia, Pa., a corporation of fennsylvania Filed Mar. 8, 1.963, Ser. No. 264,107 9 Claims. (Cl. 56-295) The present invention relates to mowing machines. More particularly, the present invention relates to improved cutters for rotary mowing machines of the type utilizing a flat blade rotating in a horizontal plane about a vertical shaft.

Mowing machine of the rotary type conventionally utilize a flat, substantially rectangular blade with the leading edges of the blade sharpened and the blade rotating about a vertically-disposed shaft. In this type of mower, the subject blade rotates at an extremely high speed, and the combination of this high speed plus the sharpening of the leading edges of the blade results in efficient cutting of grass. However, such mowers have been found to be extremely dangerous, both to the operator and to bystanders, due to the fact that foreign objects lying in the grass are struck by the blade and quite often are thrown outwardly with suiiicient force and speed to cause serious injuries. It is problematical whether objects of small size, such as wires, or larger objects, such as stones, are more dangerous. In any event, both have been known to cause serious injury because of the tremendous force with which they are propelled outwardly.

It is, therefore, an object of the present invention to provide a novel and improved cutter for rotary mowers having a high degree of safety.

A more specific object of the present invention is to provide a novel and improved bar-type cutter for rotary mowers having a substantially increased degree of safety.

Another object of the present invention is to provide a novel and improved bar-type cutter for rotary mowers having a substantially reduced tendency to propel foreign objects outwardly.

Still another object of the present invention is to provide an improved bar-type cutter for rotary mowers having a substantially reduced tendency to throw small objects, such as wires, outwardly.

A still further object of the present invention is to provide an improved bar-type cutter for rotary mowers having a substantially reduced tendency to throw large objects, such as stones, outwardly.

Another and further object of the present invention is to provide an improved bar-type cutter for rotary mowers having a substantially reduced tendency to throw both large and small objects outwardly.

These and other objects of the present invention will be more apparent from t e following detailed description when read in conjunction with the accompanying drawings, wherein:

FIGURE 1 shows a plan view of the top of one form of cutter made in accordance with the present invention and illustrating one safety feature thereof.

FIGURE 2 is an enlarged cross-sectional view of the cutter of FIGURE 1 taken along the line 22.

FIGURES 3, 4 and 5 are also enlarged cross-sectional views similar to FIGURE 2. but showing three diife-rent variations of the cutter of FIGURES 1 and 2.

FIGURE 6 illustrates another form of cutter constructed in accordance with the present invention and showing another safety feature of the present invention.

FIGURE 7 shows still another form of cutter constructed in accordance with the present invention and combining the safety features illustrated in FIGURES l and 6.

3-,l@9,2?5 Patented Nov. 5, 1963 FIGURE 8 shows another cutter constructed in accordance with the present invention and illustrating the safety feature shown by FIGURE 6.

FIGURE 9 shows another blade constructed in accordance with the present invention in which the safety features of the blades of FIGURES 1 and 8 are combined.

FIGURE 10 shows still another variation of the blade of FIGURE 8 which also combines all of the safety features of the present invention.

Throughout the present specification and claims all cutters will be referred to as having at least two fiat, bartype blades projecting radially from the center of rotation of the cutter even though such cutters have only two such radially-disposed blades and they are formed from a single flat piece of metfl. The reasons for this will become apparent from the description which follows.

FiGURE l shows one form of cutter constructed in accordance with the present invention and having two flat, radially-disposed blades 1 and 3, respectively. On the leading edge (with respect to the direction of rotation) of blade I, a sharpened edge 5 is formed. Similarly, a sharpened cutting edge 7 is formed on the leading edge of blade 3. Formed on the end of blade 1 is a narrow, ncncutting extension 9 which projects forwardly and beyond the cutting edge 5 of blade 1. A similar noncutting extension 11 is formed on the end of blade 3. It has been found in accordance with the present invention that the tendency of a bar-type blade to throw small objects, such as wires, outwardly is substantially reduced if projections such as 9 and 11 are formed on the ends of the blade. Projections 9 and 11 should not be so long as to be structurally weak and therefore break when a large object is struck, but should be sufficiently long that when a small object, such as a piece of wire, is struck by the leading edge of blades 1 or 3- and slide outwardly along the blade such wire will be caught by projections 9 and 11 before they are thrown outwardly as a projectile.

FIGURE 3 shows a variation of tips 9 and 11 in which the tip designated also projects downwardly below the bottom surface of blade 3. In this variation, tip 11a will prevent small objects which are struck by cutting edge 7 from sliding along the bottom surface of blade 3 and being projected outwardly. Similarly, modilied tip 11b of FIGURE 4 is projected upwardly and thus prevents small objects struck by cutting edge 7 from sliding along the top surface of blade 3 and being shown outwardly. Finally, modified tip 110 in FIGURE 5 projects forwardly, upwardly and downwardly and thus prevents small objects which are struck by cutting edge 7 from sliding along cutting edge 7 or the top or bottom surface of blade 3 and being projected outwardly. It will be obvious that the upward and downward projections of the tip 11 shown in FIGURES 3, 4 and 5 may be continuous projections extending along the entire breadth of blade 3 and need not necessarily be formed as shown in the drawings. It will also be obvious to one skilled in the art that tips 9 and 11 may be welded to the ends of the blades or may be formed as integral parts of blades 1 and 3.

FIGURE 6 of the drawings illustrates another safety feature of the improved cutter of the present invention. The cutter of *FIGURE 6 comprises a flat, bar-type blade 13 which is substantially straight and whose leading and trailing edges are parallel to a radius of the circle described by rotation of the cutter. Blade 13 has a leading edge 15 which is sharpened. A substantially flat blade 17 is also provided which is convex forwardly with respect to the direction of rotation. It is to be observed that noncutting extension IQ of curved blade 17 curves rearwardly with respect to the direction of rotation of end of straight blade 13. In addition, when extension 19 of blade 17 strikes a foreign object, because of the rearward and outward curvature of extension 19 the object will be struck a glancing blow and spun in a substantially stationary position rather than projected outwardly. Thus, noncutting extension 19 of blade 17 substantially reduces the tendency of the cutter to project any object struck by the cutter outwardly. A cutting edge 21 may be formed on the forward or leading edge of blade 17 but it has been found that substantially no cutting will be done by that portion of blade 17 which is outwardly beyond the center of curvature. However, some cutting will be done by a sharpened portion of blade 17 beginning at the center of curvature and extending inwardly toward the center of rotation of the cutter. By way of illustration, two blades such as blade 17 were balanced about the center of rotation and their entire leading edges sharpened. In use, it was found that such a blade out only a very narrow strip on either side of the center of rotation and did no noticeable cutting outwardly beyond the center of curvature of the blades. Accordingly, it has been found in accordance with the present invention that at least one substantially straight cutting edge such as 1-5 of blade 13 must be provided when a curved blade such as 17 is employed. However, as previously pointed out, when a substantially straight bar-type cutter such as 13 is utilized at least one other blade of the character of blade 17 must be provided, whose tip extends beyond the outermost point of cutting edge and curves rear-wardly and outwardly, in order to prevent straight cutting edges, such as 1-5, from striking foreign objects and projecting them outwardly at a high speed.

'FIGURE 7 of the drawings illustrates still another modification of the cutter of the present invention wherein the cutter is made up of bar-type blades 23, and 27. Bar-type blades 23 and 25 are substantially identical in construction and are substantially rectangular in form, having cutting edges 29 and 31, respectively, for-med on their leading edges. Formed on the ends of blades 23 and 25 are safety tips 33 and 35, respectively, which project forwardly and beyond cutting edges 29 and 31 in a manner similar to tips 9 and 11 of FIGURE 1. As previously indicated in the discussion of FIGURE 1, tips 33 and 35 will prevent small objects, such as wires, which are struck by blades 23 and 25 from sliding along cutting edges 29 and 31 and being thrown outwardly. It is also obvious that safety tips 33 and 35 may have any of the forms illustrated in FIGURES 2. through 5 and may be attached in a suitable manner or integrally formed as parts of blades 23 and 25. Bar 27 of FIGURE 7 is of substantially the same construction as bar 17 of FIG- URE 6 and includes noncutting extension 37 which curves rearwardly with respect to the direction of rotation of bar 27 and outwardly beyond the ends of blades 23 and 25. As was pointed out in connection with the discussion of FIGURE 6, extension 37 of blade 27 serves to clear away any foreign objects which might be lodged in the grass and prevents blades 23 and 25 from striking such objects. In a manner similar to blade 17 of FIG- URE 5, blade 27 of FIGURE 7 may have a portion of its leading edge sharpened to form cutting edge 39.

FIGURE 8 of the drawings illustrates still another form of cutter having the safety features previously illustrated in the discussion of FIGURES 6 and 7. The cutter of FIGURE 8 is made up of flat, bar-type blades 41 and 43, respectively. The leading edges of blades 41 and 43 lil are sharpened to form cutting edges 45 and 47, respecare curved rearwardly with respect to the direction of rotation of blades 41 and 43 and outwardly a substantial distance beyond the outermost points of cutting edges 4-5 and 47. Extensions 4 9 and 51 perform substantially the same function as extensions 19 and 37 of blades .17 and 27 of FIGURES 6 and 7, respectively. That is, extensions 49 and 51 clear away foreign objects by striking such objects a glancing blow and spinning the objects rather than projecting them outwardly at high speed. Thus, such objects will be pushed out of the path of cutting edges 45 and 47 or simply rolled over, and cutting edges 45 and 47 will not strike such objects and throw them outwardly as do conventional bar-type blades.

FIGURE 9 illustrates still another embodiment of the present invention in which the cutter is made up of fiat blades 53 and 55. Blade 53 is of substantially the same construction as blade 43 of FIGURE 8 and has a cutting edge 57 formed on the leading edge of the blade and an extension 59 which curves rearwardly with respect to the direction of rotation of blade '53 and outwardly beyond the outermost point of cutting edge 57. Blade 55 of the cutter of FlGURE 9 is of substantially the samerconstruction as blades 1 and 3 of FIGURE 1. Blade 55 has its leading edge sharpened to form cutting edge 59 and has attached to its outermost end safety tip 61. Safety tip 61 may have substantially the same form as tips 9 and 11 of blades 1 and 3 of FIGURE 1 and as such will catch small objects, such as wires, which slide along cutting edge 59 and prevent such objects from being thrown outwardly.

FIGURE 10 of the drawings shows still another variation of the safety cutter of the present invention. In accordance with FIGURE 10, the cutter is made up of flat, bar-type blades 63 and 65. The leading edges of blades 63 and 65 are sharpened to form cutting edges 67 and 69, respectively. Formed on the ends of blades 63 and 65 are extensions 71 and 73, respectively. Extensions 71 land 73 project forwardly beyond cutting edges 67 and 69 to thus catch wires or other small objects which are struck by cutting edges 67 and 69 and slide along said cutting edges. In addition, extensions 71 and 73 are curved rearwardly with respect to the direction of rotation of blades 63 and 65 and outwardly a substantial distance beyond the outermost points of cutting edges 67 and 69. This rearward and outward curvature of extension 71 and 73 clears away foreign objects by striking them a glancing blow and spinning them or rolling over them before such objects can be struck by cutting edges 67 and 59 and thrown outwardly at high speed.

It will be obvious from the prior description that other modifications and variations of the present invention will occur to those skilled in the art. Accordingly, the present invention is'limited only in accordance with the claims which follow.

We claim:

1. An improved cutter for rotary mowers adapted to rotate in a substantially horizontal plane about a vertically-disposed shaft comprising at least two flat, bartype blades extending generally radially from said vertically-disposed shaft, said blades having at least a portion of their leading edges, with respect to the direction of rotation of said blades, sharpened to form cutting edges, and at least one of said blades having an extension formed on its outermost end with a noncutting face and extending outwardly beyond the circumference of the circle described by rotation of the furthest extremity of said cutting edges of said blades.

2. A cutter in accordance with claim 1 wherein the leading edges of the blades are substantially straight and parallel to the radii of the circle circumscribed by rotation of the cutter.

3. A cutter in accordance with claim 1 wherein the entire leading edge of a first of said blades is convex forwardly, with respect to the direction of rotation of said blade, and a noncutting extension is formed on the outermost end of said convex blade which curves rearwardly and outwardly from said leading edge of said convex blade; and the leading edges of the remaining blades are substantially straight and parallel to the radii of the circle circumscribed by rotation of the cutter, and the rotation of the furthest extremity of said straight blades describes a circle whose diameter is within the circle described by rotation of the furthest extremity of said noncutting extension of said convex blade.

4. A cutter in accordance with claim 3 wherein material engaging extensions are formed on the outermost ends of each of the straight blades, which extensions have a non-cutting face and project forwardly and beyond the leading edges of said straight blades.

5. A cutter in accordance with claim 1 wherein the noncutting extension projects forwardly and beyond the leading edge of the blade on which it is formed and curves rearwardly and outwardly from said forward projeotion.

6. A cutter in accordance with claim 1 wherein the leading edges of the blades are substantially straight and parallel to the radii of the circle circumscribed by rotation of the cutter, and a material engaging extension is formed on at least a first of said blades which has a noncutting face and projects forwardly and beyond the leading edge of said first blade, and an extension is formed on at least a second of said blades which has a noncutting face and curves rearwardly and outwardly from the leading edge of said second blade.

7. An improved cutter for rotary mowers adapted to rotate in a substantially horizontal plane about a vertically-disposed shaft comprising at least two flat, bartype blades extending generally radially from said vertically-disposed shaft, said blades having at least a portion of their leading edges, with respect to the direction of rotation of said blades, sharpened to form cutting edges, and at least one of said blades having a material engaging extension formed on its outermost end which extends outwardly beyond the circumference of the circle 6 described by the rotation of the furthest extremity of said cutting edges of said blades and has a noncutting face projecting forwardly and beyond the leading edge of the blade on which it is formed.

8. An improved cutter for rotary movers adapted to rotate in a substantially horizontal plane about a vertically-disposed shaft comprising at least two fiat, bartype blades extending generally radially from said vertically-disposed shaft, said blades having at least a portion of their leading edges, with respect to the direction of rotation of said blades, sharpened to form cutting edges, and at least one of said blades having an extension formed on its outermost end extending outwardly beyond the circumference of the circle described by rotation of the furthest extremity of said cutting edges of said blades, and said extension having a noncutting face curving rearwardly and outwardly from the leading edge of the blade on which it is formed.

9. An improved cutter for rotary movers adapted to rotate in a substantially horizontal plane about a vertically-disposed shaft comprising at least two flat, bartype blades extending generally radially from said vertically-disposed shaft, the leading edges of said 'blades being substantially straight and parallel to the radii of the circle circumscribed by the rotation of the cutter, and at least a portion of said leading edges, with respect to the direction of rotation of said blades, being sharpened to form cutting edges; and extensions are formed on the outermost ends of each of said blades which extend outwardly beyond the circumference of the circle described by rotation of the furthest extremity of said cutting edges of said blades, and said extensions have non-cutting faces curved rearwardly and outwardly from the leading edges of said blades.

Moss Aug. 1, 1950 Berry May 17, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 109,275 November 5, 1963 Henry F. Dunlap et a1.

It is hereby certified that error a ent requiring correction and that t corrected below.

ppears in the above numbered pathe said Letters Patent should read as Column l line 1 1, for "machine" read machines column 2 line 48, for "shown" I read thrown Signed and sealed this 14th day of April 1964.

(SEAL) Attest:

ERNEST SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. AN IMPROVED CUTTER FOR ROTARY MOWERS ADAPTED TO ROTATE IN A SUBSTANTIALLY HORIZONTAL PLANE ABOUT A VERTICALLY-DISPOSED SHAFT COMPRISING AT LEAST TWO FLAT, BARTYPE BLADES EXTENDING GENERALLY RADIALLY FROM SAID VERTICALLY-DISPOSED SHAFT, SAID BLADES HAVING AT LEAST A PORTION OF THEIR LEADING EDGES, WITH RESPECT TO THE DIRECTION OF ROTATION OF SAID BLADES, SHARPENED TO FORM CUTTING EDGES, AND AT LEAST ONE OF SAID BLADES HAVING AN EXTENSION FORMED ON ITS OUTERMOST END WITH A NONCUTTING FACE AND EXTENDING OUTWARDLY BEYOND THE CIRCUMFERENCE OF THE CIRCLE DESCRIBED BY ROTATION OF THE FURTHEST EXTREMITY OF SAID CUTTING EDGES OF SAID BLADES. 